Posted
by
michael
on Tuesday January 13, 2004 @02:30PM
from the lead-lined-underwear dept.

AKAImBatman writes "When it comes to launching millions of pounds of material into space, nearly everyone knows about the Orion Project. Blow up a series of nuclear bombs under your dairy-aire and ride the explosion on up. Unfortunately, the Orion spewed out so much radiation that it just wasn't a feasible launch option. If we want commuter trips to space, we're going to have to find another way. Well, it turns out that NASA's been doing quite a bit of research on Gas Core Nuclear Rockets, an ultra-powerful nuclear rocket that puts out almost no radiation. This research has spurred a fascinating new generation of ideas on reaching the cosmos. Could inexpensive cruises to the moon happen within our lifetimes?"

Not necessarily. The space elevator needs equal pull on both sides of the point where it would be at the same distance from Earth as objects in geosynchronous orbit. You can either do that using a counterwieght such as a large asteroid, or by making the elevator exceedingly long, about the same length on either side of that geosync orbit position.

There's a genuine safety issue with space elevators that ought to mentioned though, which is that if the elevator breaks, the part between Earth and the break point would act as a whip. A few thousand miles probably wouldn't be a big issue, but the closer to the end the cable breaks, the bigger, exponentially, the whiplash. A shockwave that destroys significant amounts of life on Earth isn't impossible.

Basically, the elevator would be made out of a ribbon so light and with such a surface area that it would fall to the earth like a peice of paper. At least that section of the ribbon that doesnt burn up while entering the atmosphere.

A space elevator isnt like the ones you read about in Kim Stanley Robinsons Mars trilogy.

The space elevator needs equal pull on both sides of the point where it would be at the same distance from Earth as objects in geosynchronous orbit. You can either do that using a counterwieght such as a large asteroid, or by making the elevator exceedingly long, about the same length on either side of that geosync orbit position.

Admittedly, the basic ground-to-counterweight-above-sync-orbit design has great potential. But there are other designs with less cost, extreme materials, and risk.

For instance: A section of cable in low orbit, spinning end-over-end so that each end periodically dips into the stratosphere at approximately the average local wind speed. Fly up to it, hook on as it goes by, and get lifted into orbit. Balance the momentum by bringing back a payload of space-mined material on the other end.

Build it so that if the orbit decays it will break up on reentry rather than crashing, keeping its own mass low enough that it won't create another Cretaceous event by spreading tons of red-hot debris throught the upper atmosphere if it comes in. (But if you get your spin right you can design it so that it tends to be pushed UP if the active guidance fails.)

Use a near-circular orbit if you want to lift a lot of payloads to near orbit (where you can use slower engines - like ion or light-sail - to achieve high orbit or escape), or an eliptical orbit for fewer payloads to a higher initial launch.

Lots of ways to do the active guidance:
- Control the spin with currents through the cable to electron guns and collectors at the ends working against the earth's mag field.
- Small attached light sails - For orbital elements, spin, attitude, AND killing vibrations.
- Ion thrusters ditto - and you can collect reaction mass each time an end dips into the atmosphere.
- Control, solar power plant, etc. at the center, which never enters the atmosphere. (Elevator/cable-crawler to get there from the ends.)

For every load you move from high in the atmosphere to such-and-such an orbit, you sap the rotational energy of your lifter, and must add more energy to bring yourself up to speed. In the best possible case, the amount of energy you need to get your lifter back up to rotational speed is the amount of energy it would have taken you to move the load up to it's orbit without the lifter.

Which is why one operational mode is to balance the mass, momentum, and energy by using it to DEcellerate an equal amount of

"Exceedingly long" is a bit of an understatement. The length you're talking about (with just more elevator for a counterweight) is roughly 12 times the earths radius. Even with a counterweight system, the distance to geosyncronous is almost 6 earth radii. So, aproximately, you need a cable that completely encircles the earth when laid flat, and is strong enough to support its own weight when hung on end. I don't see that kind of strength-to-weight ratio being produced any time in the near future. And e

I don't see that kind of strength-to-weight ratio being produced any time in the near future.

Pure carbon nanotubes have the required strength-to-weight ratio. The only question is how long before we can develop a composite that binds CNTs together into a material that retains enough of the strength of pure CNTs. Steady progress is being made. Keep an eye on LiftWatch.org [liftwatch.org] for regular updates on this and related techs.

Umm, what happens if it breaks somewhere high up? I can't imagine I would want to be anywhere near where the "stalk" came crashing down. Don't get me wrong, I am not real keen on nuclear filled rockets that could explode on or soon after launch either.

Somewhere, long, long ago, architects were sitting around talking about this huge, incredible building that would be a real monument to captalism and a center for world trade.

Someone said "wait... what if something smacks into it? If it hit it hard and high enough, the impact could severe the support in the building and bring enough material down fast enough that the rest of the structure would implode. That's a lot of steel and concrete falling an awful long way!"

No one said that. In fact, when that question was asked, the answer was "Okay, so we have to build it strong enough so that can't happen." And they did - the WTC was capable of withstanding an impact by the largest jet transport that existed at the time of its construction.

In fact the WTC towers were capable of (mostly) surviving 9/11, if only there had been better fire retardants on the supporting columns - which had been recommended repeatedly, particularly after the 1993 attacks. Nobody said that was a worry for another day, either, they just didn't want to pay for it.

Try breaking the cable high enough above the planet that the counterweight exits Earth orbit.

Okay, I can see that being easy.

Now, imagine TIMING such an event so that the counterweight ends up headed right for a lunar base.

I can't see that being easy, though. It depends on an impressive list of things, foremost amongst them is there being a lunar base in any sort of position to be hit by the counterweight. It's not like you can aim; all you can do is time the break.

Incidentally, the earth has an angular momentum of about 9e33 kg-m^2/s (I might be off by a factor of two), for all those interested. For comparison, a 6000 pound (about 3000 kg) truck moving 30 m/s (about 70 mph) only has an angular momentum about the earth center of about 6e11 kg-m^2/s. A 10000kg spacecraft moving at 3000 m/s at 30000 km altitude, though, has 1e15 kg-m^2/s. Launching one spacecraft - just ONE - at this rate will take off about 4e-12

Ok...I'll give you that. To get into space, a space elevator is probably a better idea. Two reason to continue developing nuclear engines:

1) We don't have space elevators. Simple as that. Until the day they are reality, we need something better then conventional rockets.

2) Once in space, either through the use of these rockets or a space elevator, these would be extremely useful for getting around the solar system, or at least roaming our backyard (the moon) or visiting next door (Mars).

IANARS (rocket scientist), but I enjoy learning about developments in space tech. The nuclear engine, while different versions having been developed and tested decades ago, still looks to be the next best thing in space travel.

Also, building the space elevator involves moving insane amounts of mass around, both up from earth and in from elsewhere in the solar system (e.g., Luna or the asteroids). The space elevator would be several orders of magnitude more massive than the combined total of everything ever sent into space to date, and that's even if you count each Shuttle launch separately. There's no reasonable way to build a space elevator without nuclear propulsion.

Actually, a SE makes a significantly better, safer and cheaper inter-solar-system-transportaion-system than dirty bombs. It's not just a tool to escape orbit - it can take us to other planets. That's what's so genious about the idea.

There are two reasons for making it 91000km long when all you technically need is 35000km.

One: because you need a very large and unfeasible mass at the top if you want to balance 35000km of cable hanging below GEO with a weight located, say, 1 meter above it. You need a significantly smaller weight at the top if you want to balance it at 91000km.

When you can build a 40,000-millimeter suspension bridge out of carbon nanotubes and cross the river near the campus materials lab building, then you can start fantasizing about a 40,000-kilometer space elevator.

Until then, NERVA is the only way to go. Everything else is still at the research stage.

I think you need to have a look at Liftwatch [liftwatch.org]. There are a lot of announcements such [liftwatch.org] as [liftwatch.org] these [liftwatch.org]. There are nanotube advancements almost every month, and a whole bunch of universities and corporations worldwide are throwing rather large sums at putting it under heavy research. A 1km cable with 2% CN loading was already constructed a while ago. Smaller stretches were already made with 5% loading at the time the NIAC phase II was written, and was mentioned in said paper.

You neither need to grow a 35000km buckytube, nor do you need to reach a 100% CN-loaded ribbon.Composites will be made with a higher and higher CN loading, and once a certain percentage is reached (feel free to check the NIAC 2 paper [spaceelevator.com] which draws this line quite clearly), you'll have elevator-worthy material. At the rate CN loading in composites has been increasing in the past decade or so, we should [hopefully] have elevator-worthy material in about 2 years.

Funny, all the old space probes had nuclear powerplants and that all worked out just fine.

This is an education issue mainly.

If people can believe we have designed black boxes that survive being slammed into the Pennsylvania crust at 400 mph or the disintegration of its containing shuttle at 30000 feet - why is it a stretch to believe we can make a containment system for fissile material that would survive even catastrophic launch failure?

So how big is a reactor core? Forget about making your entire satalite out of something that can survive any inpact/re-entry, and build just the core container. You don't never need all the connections that good, so long as your core is designed so it can't explode (not a big deal). Satalite breaks up, but it protects the reactor core while it does so, then the core in the small strong box falls to earth and is recovered.

Remember when Cassini went up, with a little thermal nuclear battery? It would have taken something like a direct DU antitank round to split that casing; a crash never would have done it.

NASA pointed this out, repeatedly, and stated the very safe history of these devices. Nevertheless, there were swarms of people protesting at NASA. They showed footage of families with children crying; the parents had told them that the rocket was going to crash and the radiation would kill them all.

You can't reason with these people any more than you can reason with conspiracy theorists. They know what they "know" and if you tell them different, you're a god-damn liar.

This is the same reason that NMR is now called MRI. Nuclear bad, magnets good! If they put that magnet inside a pyramid, people would pay to sit inside it for no reason.

The big problem (which, IMAO, was a real issue that got glossed over in the propaganda wars about the launch) was hypervelocity impact if the probe accidentally hit Earth during the Earth-flyby gravitational boost.

Cassini, if I recall right, was to go inward to Venus for a gravitational assist, then fly by Earth again for another boost before leaving for the outer solar system. Because the trajectory was only marginally possible to begin with, they had to come rather deep in the gravitational well -- only 200 or 300 miles above the top of the Earth's atmosphere.

During that flyby, Cassini was traveling well above Earth's escape velocity of 10 km/sec. I never saw anyone seriously claim that the plutonium would have remained contained in case of impact.

NASA's response to that point was, essentially, "We don't hit planets by mistake". That was good enough to avoid the various court orders and injunctions that were being cooked up, but it might not suffice today. A few months after the Cassini flyby, NASA (or JPL or Lockheed, depending on whom you ask) did hit a planet by mistake, when the mars probe impacted instead of aerobraking.

On the other hand, the protestors' argument that there was enough plutonium on board to kill half of the Earth's population, if properly distributed, is sheer alarmism. Almost every Slashdot reader generates weekly enough of a certain other substance to, if properly distributed, impregnate half of the Earth's population. Yet only a tiny fraction of children are descended from slashdotters.

It isn't a stretch to believe we can build safe nuclear power sources because the US has been building safe RTGs for 40 years. From this [nasa.gov] link:

The objective of current U.S. RTG design philosophy is for
full fuel containment; that is, in the event of an abort
during the launch or on-orbit phase of a mission, the RTGs
are designed to retain the fuel material. In two subsequent
unplanned incidents involving U.S. RTGs, the new design
philosophy successfully prevented the fuel from being
released. The first involved two SNAP 19 RTGs in a 1968
meteorological satellite while the other involved one SNAP
27 RTG in the Apollo Lunar Scientific Experiment Package
(ALSEP) aboard Apollo XIII in 1970.

Neither of these
incidents caused release of radioactive materials. The two
SNAP 19's were recovered from Santa Barbara Channel five
months after the range destruct of the launch vehicle. The
nuclear fuel was reprocessed and later re-launched in new
RTGs. No release of the fuel was detected. The mission
abort maneuver of Apollo XIII separated the Command Service
Module from the Lunar Module. The Lunar Module containing
the SNAP 27 RTG (as part of the ALSEP) re-entered the
atmosphere and impacted in the South Pacific Ocean in the
region of the Tonga Trench, where it remains today. Air and
water samples taken by the U.S. in the vicinity of the re-
entry found no evidence of fuel release.

That is right, the US self-destructed a rocket right after launch and the RTGs survived intact, were recovered and the material was in good enough condition to be reused.

Nuclear propulsion is our ticket off this rock. The only thing in our way is ignorance of the technology.

Where the reaction begins has no bearing on the danger the reactor poses; again, it's an education issue.

The danger in the event of catastrophic failure comes solely from a possible dispersal of the fissile material.

We have reactor designs now that simply can not result in the reaction going critical. It'd actually be much safer now than it was in the 70s.

The only reason you're not allowed to talk about these things, even to educate the public, is the same reason you're not allowed to promote nuclear power generation. It's simply career suicide for any public official to broach the subject.

Provided the radiation from their rocket stays at what the specs suggest, this is no more inherently dangerous than the operation of any of the dozens of nuclear reactors currently commissioned in the united states. (not counting nuclear naval craft)

The public's irrational fear of all things nuclear is the only opponent that killed nuclear technology. It has nothing to do with actual science or statistical risk.

It has nothing to do with the tonnes of nuclear waste produced for which the only solution seems to be "put it down a large hole, that'll do" then?

Or perhaps my irrationality extends to thinking that when the pigeons around the UK's nuclear waste processing plants are so radioactive they would be classed as nuclear waste [greenpeace.org] themselves if they were inert. Internal contamination of the pigeons was found to be beyond safety levels set by the EC in the aftermath of nuclear accidents.

The problem with nuclear power is that it is made by humans and they have a habit of fucking up on a grand scale.

the tonnes of nuclear waste produced for which the only solution seems to be

"stick it in a
fast [nationalcenter.org]
reactor [berkeley.edu]
and use it again".

except that made the know-nothings even more scared of their own shadows, so politics and fear-mongering killed that too.

Or perhaps my irrationality extends to thinking that when the pigeons around the UK's nuclear waste processing plants are so radioactive they would be classed as nuclear waste themselves

if you think that proves anything about nuclear waste reprocessing as such, then you would indeed be thinking irrationally. if, however, you get a sneaking suspicion that the simple explanation - namely, that whoever operated that particular plant were a bunch of goofball morons who shouldn't have been trusted to operate a toaster - might after all be more likely, then perhaps there is still hope for your rationality and sense.

The problem with nuclear power is that it is made by humans and they have a habit of fucking up on a grand scale.

how, exactly, is that a problem with nuclear power?

that is a problem with people. don't blame nuclear power for your belonging to a race of goofball morons. if you let humanity's inherent flawedness scare you away from doing anything at all remotely dangerous - because, ohmygoddess, we might fuck it up somehow, because we are so goddamn motherfucking stupid, we can't trust ourselves with pointy sticks even, we might poke our eyes out, won't somebody think of the children - then nothing will ever get done. at all. by anybody.

yes, nuclear power carries some risks. so does every other damn thing you will ever think of. as a general rule of thumb, the more worthwhile and useful things you can think of will be proportionally more dangerous. that's life - deal with it.

And would dispersal be greater if the nuclear reactor went critical?! Thought so...

Here's where education is important. Do you understand what "going critical" is? Very specifically, it's a build up of heat from a "melt-down". (A "melt-down" being when a nuclear reaction gets out of control and produces excessive amounts of heat.) Usually reactors are highly contained units. All that extra heat builds up pressure that has to go somewhere. Thus the containment itself can produce a big explosion. Still, it's more like an industrial boiler exploding than a nuclear bomb. The only radiation is from any radioactive material that gets ejected. (Usually not much, and cleanup isn't too large of an issue.)

Now in a nuclear rocket, specifically a Nuclear Thermal Rocket, heat is what we want. Assuming the reaction goes beyond the safeguards (which should be impossible), you can simply increase power to the turbopumps and flow more fuel through the reactor. This will end up providing far more thrust than originally intended (read: serious KICK IN THE PANTS), but the melt-down will not become critical.

"going" critical: All nuclear reactions (not nuclear decay) are critical. In order for a self sustaing nuclear to occur, a critical mass of fissible material must be present. If the mass falls below critical the reaction will extinguish. Decay will still occur and generate heat, abliet much less.

Melt-down: A melt-down happens when a reaction goes out of control and produces sufficient amounts of heat to cause the core the liquify (melt down). When a core melt-down happens, there is not a damn thing on this planet (that I know of) that can the molten (and getting hotter by the second) glob that used to be the core.

It has been theorized that if this happens, the molten core will burn through the earth until it reaches water. Upon contact with the core the water will turn into steam and create what is in effect a steam cannon, blasing the core back up the hole and showering bits of the core for miles around.

When a core melt-down happens, there is not a damn thing on this planet (that I know of) that can the molten (and getting hotter by the second) glob that used to be the core.

It has been theorized that if this happens, the molten core will burn through the earth until it reaches water.

part(s) of the core of Chernobyl 4
melted down. [kyoto-u.ac.jp]
(though i'm not entirely sure if this was due to a runaway reaction producing too much heat, or due to external heating from the graphite moderator fire started by the ste

Yes, actually reactors must go super-critical just to get started. This just means that the reaction rate is increasing. When you get to the operating level you want, you push the rods in until the reaction slows to a critical level.

As far as meltdowns go, you forget one thing. As the core melts surrounding materials, it mixes with them and this causes a certain amount of moderation, slowing down the nuclear reaction. Many new reactor designs incorporate moderating materials directly into the containmen

If going "critical" means that it has gone beyond the safeguards and is melting the containment safeguards (which is what I meant..) then who's to say the pumps (or any other piece of equipment) wouldn't just melt?

Because the Turbopumps are in a different part of the craft. Did you read the article? Turbopumps push a steady stream of fuel from the tanks to the core where the core heats the material to PLASMA. Don't suppose you know how hot plasma is, do you? I'll try to explain it this way: The reactor is DESIGNED to run under what would be considered melt-down conditions in a normal reactor. More heat from the reactor means more energy transfered to the fuel, which means more thrust. If you cut the thrust, the backend of your rocket will melt and fall into the ocean. The ocean will provide a new moderator that will stop the reaction completely. The reactor will still be contained in its shielding, so little to no radiation will be exposed to the underwater environment. (Not that underwater volcanos don't already put out enough of that.)

But that's all besides the point, the point was, if it DID go critical, and it DID explode, that would be inherently WORSE then if the shuttle just blew up.. You said:"Thus the containment itself can produce a big explosion"

Doesn't that one statement agree with what I'm saying?!

No. Because you took two different designs and equated them. Nuclear engine != Nuclear powerplant. A powerplant exists under pressure. It can only operate within certain heat tollerances before a boiler explosion (and it IS a boiler explosion) happens.

A nuclear engine exists in a state where ALL the heat is being transferred to fuel. More heat is actually a GOOD thing in the engine as it provides more thrust. The problem with a runaway reaction (which doesn't just happen by itself, sorry to say) is control. You're now sending your astronauts on a trip to the moon when all they wanted was to achieve orbit. That's a problem. In many ways that's less of a problem than a failed chemical booster which would simply explode, or fail, or just about anything else. Assuming the craft survived the initial failure (not likely), a chemical booster helpfully drops you back to Earth at terminal velocity, on an unknown vector.

With a little education, you should be MORE scared of chemical rockets than nuclear ones.

Chernobyl? No cause for alarm... Three Mile Island? Hiroshima anyone? What about a "dirty bomb?"

Quite irrational. Chernobyl was an inherently flawed reactor design. It can't happen in our superior reactors. Anyway, it didn't kill all that many people. TMI didn't kill or injure anyone. And a dirty bomb's radiation wouldn't cause very much harm. The blast would be the main thing. And hiroshima. Fuck. That's a bomb designed to kill people! Of course its dangerous.

Oh, and once you're done telling me how safe modern nuclear reactors are, let's go on the tour of Hanford together, okay? I'm counting on you to hold my hand during the scary parts, like when the nuclear waste enters the water table.

I live just a few miles away from Hanford. I don't know where the fuck you get your news, but the radiation at Hanford isn't harming anything. The place is a wildlife preserve, one of the best shrub-steppe desert habitats in the wast. The radiation from the waste leakage is inconsequential compared to what you get from the sun every day.

Nuclear power, historically, has been very safe. Certainly compared to coal power, with its smog and mountains of toxic coal waste. Don't listen to idiotic ultra environmentalists.

Hanford's tanks full of nuclear goo are going to rupture "any minute now." The problem with nuclear waste is that "any minute now" means "any time in the next 20,000 years."

It's not so much the reactors that scare me, it's what do we do with the shit they create? With coal, we get pollution and global warming. With nuclera, nobody really seems to know what the fuck to do with the stuff.

But you are right, any problems at Hanford stem from making nuclear bombs, not from nuclear power. Nulcear power is s

Exactly. Let's look at the facts, shall we? Chernoby was (is) old Soviet-desgn reactor. Those reactors do have a risk of catastrophic failure (like Chernobyl) it can NOT happen in moder western-type reactors (had similar thing happen in a western reactor that happened in Chernobyl, the reactor would shut down. No fire, no explosion, the reactor would shut down). Also, the technicians in Chernobyl basically did everything they could in order to blow the thing up. They removed t

Because you can hit a black-box recorder with your shoe for hours, and it won't explode and take the whole state with you.

How do you people come up with this stuff? "Explode and take the whole state with you"? From kicking it with your SHOE? You'll have to forgive me, but I can't believe ANYONE would make that statement!

Ok, Nuclear Physics 101. First and foremost: Fissionable materials are not inherently unstable. In fact, Uranium and Radon are naturally occurring substances that a lot of people live on top of. Now you get a "nuclear pile" when you put a lot of material together. The nuclear material spontaneously fissions on occasion (no, I'm not making this up) producing fast moving and slow moving neutrons. The slow moving neutrons will tend to hit other atoms. If a hit occurs just right, it will cause other material to fission. Heavy materials work best for this as their sheer mass makes them easier to crack.

BTW, there isn't usually enough slow neutrons to produce a nuclear "critical" reaction (i.e. produce any amount of power or heat). Water is usually used to slow down fast neutrons and produce more fissions. With enough fissions, a reactor can get a stable "critical" reaction going. Today's reactors are built to evaporate the water if the reaction gets too hot. Thus a melt-down stops itself. Older reactors kept everything under pressure, so if the reaction got out of hand, you'd end up with a BOILER EXPLOSION. That's right, let me repeat myself, a BOILER EXPLOSION. Those aren't great, but they hardly take out a large area.

As an example, Chernobyl killed 40 people on site. That's it. The remaining 3 reactors at Chernobyl kept running for decades. (Which they shouldn't have, but that's another problem.)

Now, a nuclear bomb is carefully designed to produce what's called a "super-critical" reaction. A super-critical reaction is only obtainable by very careful manipulation of the fissibles. Atomic bombs have shaped charges that force all the neutrons inward and (hopefully) cause most of the material to fission all at once. That produces enough force to take out about a city. For a really BIG explosion, special reflectors and materials are used. First an atomic blast is contained within a tiny bomb. Nearly all the energy is reflected inward by a uranium shell. That much force in a confined space (at a temperature about as hot as the Sun) then forces hydrogen atoms together into a material we call Tritium. The result of this is much more energy than the original blast. Enough to take out a small state or country.

Now, let's take the nuclear challenge. I'll give you a black box of rocket fuel to kick around. I'll take a black box nuclear reactor to kick around. Whoever survives the longest wins. Want to take me up on it?

But unfortunately, the space elevator will be so obscenely expensive in terms of resources and labour to get going in the first place that though amortized over a large number of launches, the cost would indeed be low... they probably won't be willing to wait that long to recover their costs, so launches that way would be even more expensive than the methods we use currently.

You are being bombared with deadly radiation right now! Coming from the ground, objects in your home, and worst, from mankind's eternal nemesis, the Sun itself. Please flee your home screaming and head for your nearest all-lead fallout shelter!

One of the biggest problems with anything Nulcear, be it power, subs, or rockets, there is a very negative public perception. You can tell people that it is safe all you want but there will always be that paranoia. It doesn't help that people don't neccesarily trust the government.

All very true, but measuring the volume of toxic waste is not really the point. The kind of stuff we have to deal with from nuclear power plants is nasty. WAY nastier than anything which comes out of a traditional power plant. Stuff which is so nasty we have no idea how to deal with it safely. All the plans to bury stuff in X tons of concrete under Y miles of rock are to my mind amazingly naeive, assuming as they do that we can accuratly predict the geology, tectonics, water flows etc thousands of years into the future. I have a real problem with any plan which involves hiding a problem away and hoping that a future generation will figure out how to deal with it. Not that coal/oil/gas are perfect, we are of course storing up problems for future generations there, but the risks seem more manageable.

Not to mention the fact that your average coal burning plant simply doesn't have the potential to cause a catastrophe on the scale of Chernobyl, Three Mile Island, etc. Nuclear power is great except for (a) the waste and (b) the very rare but very destructive accidents. Once (a) and (b) can be dealt with more sensibly I'll be a supporter.

The kind of stuff we have to deal with from nuclear power plants is nasty. WAY nastier than anything which comes out of a traditional power plant.

Which is why we have to figure out how to get the stuff into space cheaply so we can jettison it into the sun. No geology to think about. No tectonics or water flow, just pure fusion energy cooking the bejesus out of our toxic waste.

"Not to mention the fact that your average coal burning plant simply doesn't have the potential to cause a catastrophe on the scale of Chernobyl"

Not all at once in one place.

Coal and Petrochemical based air pollution has killed tens of thousands to hundreds of thousands at younger ages than they would have otherwise died, and cars and tobacco have killed TENS OF MILLIONS of people this century, and yet you think that the HUNDREDS of reactors in current operation in North America whom haven't killed a SINGLE HUMAN BEING yet - are a bigger badder threat.

Stupid dumb public. And they bitch like hell when we try and keep their asses in High School all the way through until grade 12.

Doesn't this discount all of the pollution billowing out of conventional fuel smoke stacks regularly every day? Certainly just because all of the harm isn't caused by one single huge incident doesn't mean their aren't terrible results of it. Skin cancer caused by Sun exposure in areas where the ozone layer is depleted is one example I can think of. What about acid rain, toxic waste poured into rivers, and the strip mining to get coal?

I know it would be terribly hard to come up with a side by side compari

The kind of stuff we have to deal with from nuclear power plants is nasty. WAY nastier than anything which comes out of a traditional power plant.

Sometimes. Sometimes not. On my college campus there was a small (6 MW IIRC) nuclear reactor, used for instruction in the Nuclear Engineering courses. I took a tour of it once (I was in Chem E, not Nuc. E, so I never got to do any actual work with it) and heard an interesting story from one of the professors there.

They were doing a scheduled test one weekend of some of the safety systems, so they were expecting some alarms going off. One of the students walked in the door, and suddenly all of the radiation alarms went off. They got out their gear and traced it down to the student who had just walked in. Specifically, they tracked it down to his head. So they got a 55 gallon drum of water and started washing his head. After a little bit of that, the water was radioactive, but his head wasn't. After they were finished, he told them what he had done. He had gone to WalMart and bought a wick for a coleman propane lantern. He took some scisors and cut it up into fine pieces, and sprinkled it on his head (The wicks are coated with a chemical which gives it a cleaner, whiter light, and also happens to be slightly radioactive).

The amusing thing about all of this is the contrast between normal use and a nuclear power plant. 99.99999% of the coleman wicks that are sold are thrown away in the trash (or littered with near campsites) because they really are not a hazard to anyone, and no sane person would say they are. However, because he brought the one he bought into a nuclear power plant, the plant had to classify the whole 55 gallons of water as potentially dangerous nuclear waste, and they had to spend a fairly large amount of money to have it disposed of "properly". How much of the nuclear waste that's being encased in concrete and buried under miles of rock is more (or less) dangerous than what you can buy in the local WalMart?

I'm not worried about the clean launches. What I'm worried about is the very dirty explosions (UF4 all over the place). I agree with the previous poster on spending money on the space elevator. Lets skip the flying dirty bombs.

I think it's great that the we are still seeing innovation in regards to propulsion for space-bound vehicles. I'm especially excited about the new concepts used in the Vostok [videocosmos.com] booster-like series that the Russian space agency is evaluating.

We're definately a long way from the V2 when some simple hydrogen would be ignited, and then Bob would be your uncle.

Radiation can be beneficial and should not be feared. Of course there will be some potential for accidents and some minor radiactive pollution, but it's all worth it in the case of scientific progress. We don't have clean water or clean air, and you don't city inhabitants rioting, or do you?

on Gas Core Nuclear Rockets
those have been around for years, and i have been fortunate enough to work with them for much of my life. they are called bean burritos. there is more explosive energy in one of those bad boys than most realize, especially when the chemistry behind the force is just right...granted, the fallout is pretty terrible too...

A few years back, I remember there being some amazingly loud protests from some anti-nuclear power folks about the dangers of a deep space probe going up with a nuclear power source. Those folks were worried about the danger if the rocket blew up on the pad or the 1 in 100,000 or so chance the probe would hit the earth on one of its acceleration orbits.

Just imagine how happy these folks will be with a nuclear powered rocket, even if the scientific community claims that they are safe. After all, it's nuclear related, so it's gotta be bad!! (tongue firmly in cheek)

What the protesters didn't tell you--probably because they couldn't be bothered enough to research they'd know this-- is that (1) we'd been putting up reactors on spacecrafts for years and years and (2) the reactor was one of the most mind-bogglingly safe imaginable, if the entire reactor was blown up or disentigrated in the atmosphere the radioactive material would still be able to hold together well enough that at worst it would split together into a couple of chunks so solid you could pick them up and hold them...

My suspicion is that Nuclear technology will get nowhere in the United States until people stop calling it that, due to the huge political movement to make sure no one uses anything with "nuclear" in the name, regardless of the safety, degree of research, or degree of oversight. I'd propose scientists start using some other word, like "happytronic", but this would probably be seen through as "hollow PR from the nuclear industry". (That's another thing. People promoting nuclear energy are often derided as "Nuclear Industry Shills", but people attacking it are never successfully labelled as "Coal Industry Shills", despite the fact that's who they're primarily helping. How is this?)

This is the primary promise Fusion offers IMHO-- because oh, it isn't nuclear, it's "Fusion", right? Which means people will actually use it.

Perhaps we should start researching some kind of "hybrid" technique, which would allow the creation of reactors that can be claimed to be "fusion" although they're actually just fission reactors with some kind of technique involved that has something vaguely to do with fusion.

i wouldn't say we have a problem with nuclear so much as a problem with non-military nuclear. and i have a feeling it's because we're the only ones who've actually used nukes against anybody -- we've got this stigma, this association between 'nuclear' and 'bomb'. can't be used for anything else now. coal (etc.) industries are more than happy to play off that fear, but i think the public fear came first. it can't have helped that we liked to scare ourselves with nuclear mutant monster movies...

on the other side of the pond, you'll find countries like france who have quite the nuclear arsenal as well (as i recall, france has more of a nuclear arsenal than china, and is third or fourth in the world?) but also get the vast majority (74% or so? that was in my high-school days) of their power from nuclear plants. and they're not worried about it. it was also france that had, what was it called... super-phoenix? to burn the waste from normal nuclear plants to produce extra power from it, along with a different kind of waste, i believe. i do remember the local villagers didn't care for that project too much (what with shipping nuclear waste into the town on a regular basis!) in any case, they don't really mind nuclear power, though they would (from what i can tell) slightly prefer hydro-electric power.

germany, on the other hand, is heading to dismantle and sell its nuclear reactors in favor of... something else. so long as they don't go back to coal, eh, whatever. seems to me the north shores of germany would be an excellent place for hydro-electric power.

it is very much a problem of perception. just don't use the words 'radiation', 'emission', 'atomic', 'split', 'neutron', 'proton', 'electron', 'blast', 'coil',... in the new name. wait, are we afraid of anything technical-sounding? "super-efficient steam engine" maybe?

What the protesters didn't tell you--probably because they couldn't be bothered enough to research they'd know this-- is that (1) we'd been putting up reactors on spacecrafts for years and years and (2) the reactor was one of the most mind-bogglingly safe imaginable, if the entire reactor was blown up or disentigrated in the atmosphere the radioactive material would still be able to hold together well enough that at worst it would split together into a couple of chunks so solid you could pick them up and ho

I highly doubt it. As the last twenty years have shown, it's not the level of technology that determines how easily we get into space, it's the cost. And concepts such as these, while interesting to think about and develop, are ultimately going to take that many more decades to become proven.

Add to all this that the public would need a near-100% safety record in order to buy into a space tourism industry, and we're looking at more decades added onto the R&D and testing.

However, this kind of engine if developed properly COULD lower costs for putting satellites in orbit. So what's our benefit in the end? Lower satellite TV, telephone, and internet costs perhaps... But that's being optomistic.

America loves its legends. George Washington in Valley Forge. The Wild West. World War II. The Man on the Moon.

But lately, it seems the legends have stopped.

Sure, we have the Internet to play with now, and computers are changing the world in ways we can scarcely grasp as of yet. The Soviet Union is no more, and despite our current travails with terrorism, a certain comfortable familiarity has us in its grip.

Where is the next legend? Where is the next frontier? Or are we just going to go comfortably off into retirement?

If the 'entertainments' of the kids these days are any indication, no way.

Extreme sports, fun little things like 'base jumping' and other diversions indicate that the next generation of Americans are harkening back to their roots in a big way. America is ready for the next challenge, refreshed, revitalized, and shaking off old fears and inhibitions.

But what could have caused our recent doldrums?

Why have we not gone back to deep space, that logical 'Final Frontier,' for so many years after Apollo? I believe it was a confluence of several factors, most of which have now passed, that caused us to huddle close to the bosom of Mother Earth for these past decades.

Part 2: What went wrong.

To be blunt, it was the 70's.

After the turbulent change of the 60's, the 70's were just a hard time for America. The Cold War dragged on and on, no end in sight. Vietnam was a horrible, bloody mess, deeply misunderstood to this day, and bitterly divisive even in the aftermath. Watergate destroyed the faith of millions in their own government. The Oil Embargo shocked the economy as well, causing the nightmarish condition of 'stagflation.' Cultural upheaval became the norm as gains in civil rights were cemented into place.

With that litany of bad news, there is little wonder that the public lost interest in space. When you are scared for your job, your children, and whether or not your paycheck next year will still cover the rent, idealism and exploration goes out the window.

Also, lets be honest, landing on the Moon in the 1960's was an incredible feat. That entire rocket, the whole plan, was designed, built, and flown using less computing power than you have in your PC. Genius level effort was used to make that program possible, and the chance of disaster was perilously high, even by the comparatively relaxed standards of the day. In other words, Saturn was ahead of its time, by many years.

If it wasn't for the Cold War imperative to beat the Soviets, we'd probably be looking to go to the Moon right about now, all things considered.

Add in the fact that science itself was throwing up massive roadblocks, and there is little surprise to be had from the seeming 'retreat from space.' The rocket fuel used in the Saturn V moon rocket at launch was BETTER than the rocket fuel used to launch the Space Shuttle today. Why is that? Well, it's simple: The chemical fuels used in the Saturn V are among the best fuels that chemistry allows. Science is remarkably inflexible: unlike in the movies we can't just 'whip up' better rocket fuels. Chemistry is pretty stubborn that way.

So, exploring further in space was not important to the country while we had other problems to deal with, and making rockets better than the SaturnV was pretty much impossible.

So, NASA went sideways for a while. The Space Shuttle is a remarkable system, but it is at its core a compromise. So while it is good at many things, it is great at nothing. But nonetheless, the Space Shuttle kept America in space, and slowly we were building momentum to move forward once again away from the Earth.

Then Challenger blew up (and now we've lost Columbia and her crew as well).

Now, to the doughty folks who made Apollo fly, that disaster would have been a learning experience, and development would have continue

My understanding is that the clean nuclear propulsion systems presently under serious consideration don't provide a high enough thrust/weight ratio to actually lift a spacecraft off the surface of the Earth. Rather, their primary use would be for entirely space-born craft, which would be assembled in orbit and zip around the solar system without actually ever touching down anywhere.

In fact, ion motors, and proposed fusion motors (google for "inertial confinement fusion" and "magnetic confinement fusion") have a very high Isp (3000 seconds for ion motors, up in the mid 100,000 seconds for fusion motors) but generate very low thrust.

The stream of particles these motors produce move very quickly, but there aren't a lot of them.

Allow me to rephrase. NERVA got up to 75,000 pounds of thrust out of the TEST rockets. The GCNR rockets are far more efficient, plus we can boost efficiency by use of particle accelerators on the plasma. Thus we can get MORE THRUST with THE SAME REACTION MASS that is used for chemical thrusters.

Think of the nuclear rockets as ultra-powered chemical rockets. Somehow we've managed to get the hydrogen to higher velocities than was previously possible with a simple chemical reaction.

BTW, Force = Mass * Velocity2. So more velocity at the expense of mass will improve our thrust. Obviously there's an upper limit to how much velocity we can obtain, so we need to throw more mass. But if you consider that a nuclear engine can throw the same amount of mass as a chemical engine (minus some "light" electrons lost in plasma conversion), then we have greater overall force coming from our nuclear than our chemical reaction. Although, to be exact we're both throwing and pulling against the plasma. First we create the plasma which is exhausted (throwing). Then we use EM accelerators to pull on the plasma on the way out. The "pull" transfers that much more energy from the mass to the craft.

That being said, I am NOT a rocket scientist, so I can't give you exact numbers. However, the article I linked to in the story does give quite a few numbers, and a bit of googling will produce even more exact numbers. (I've seen some right down to the force per molar mass on usenet. Since I wasn't going to be building one of these things myself, my eyes kind of glazed over at that.)

Most people go batshit whenever they hear the N-word. That's why NUCLEAR Magnetic Resonance Imaging had to lose the N before it could go mainstream. NMRI became MRI for PR purposes, not because the technology changed.

The environmental whackos go nuts (and let slip the lawyers of war) when you launch a totally sealed reactor, can you imagine what they would do if you wanted to launch something that *gasp* released radioactive gasses into the atmosphere?

The Project Orion guys believed they could makethe explosions clean and as small as they wanted.This scared the shit out of them. Theypuposefully did not pursue that line ofdevelopment for fear of weapons applications.

The Project Orion guys believed they could make
the explosions clean and as small as they wanted.
This scared the shit out of them. They
puposefully did not pursue that line of
development for fear of weapons applications.

I call bullshit.

Source, please. Some relevant links would be nice. If you turn out to be right, I withdraw my bullshit call, but otherwise it stands. I don't recall ever reading anything like this.

A gas core nuclear reactor has a high ISP (meaning it's very efficient), but it does not have a particularly high thrust. That means it's great for cruising and orbital work, but it's not a launch engine like Orion could be.

Nothing is permitted any more without a "business case" being made for it. No document, no invention, no idea, no presentation is countenanced unless it has 20% annual growth and the accountants and the management committee sign off on it.

Since it is impossible to get a bureaucracy to sign off on anything, nothing is permitted at all.

Small businesses and entrepreneurs are starved for capital. Large businesses and management committees have substantial capital, but refuse to invest it. Therefore, there is no capital; or, if there is, it is usually totally inadequate.

Middle management has a perfect series of questions for ideas like this. There is nothing in the world easier than criticizing an idea. Questions like "what do we need that for?" and "yeah, but how do you know it will work?" or "how can you be sure that will sell?" These questions are asked as if an answer is expected. The questions are followed by the comments: "It'll never work," and "sounds expensive" and "why can't we just use $OTHER_IDEA?"

But no answer is expected. The people asking the questions simply want to see how well the "idea person" can ad lib and how many bullshit one-liners and jokes they can reply with. After the middle managers have been entertained, a cocktail party laugh will circle the room, and the idea person will be escorted out of the building and into obscurity as the five-foot-wide-asses return to their bean salads.

As long as this continues, the rate of invention and "innovation" will be reduced to unmeasurably small levels. No vision, idea or invention can surmount well-funded cynicism. Brilliant, well-educated people's minds are being wasted because they report to lying, cheat fuck, greed-driven managers.

Middle management routinely turns its back on paying customers and competition-less markets. How the fuck are they ever going to accept a new "unproven" idea?

Besides, nobody's going to be sending a nuclear rocket into orbit anywhere near me, so I don't mind. Let the Floridians suck it up! They're already addled from all that solar radiation beating down on their pates and overheating their brains - a bit more won't make much difference...

I'm guessing that telling some of the more extreme environmentalist elements that your launch puts out "almost no radiation" isn't going to hack it as far as they're concerned. 1 microrad/hr above background will be reason enough to predict apocalyptic nightmares of mass cancers, food contamination, mutations, dropsy, genital warts, and flatulence. They're essentially anti-technology and will use any excuse to oppose it. Frankly, I'm surprised I can still buy a radium-dial wristwatch.

This called for a 40-million-ton spacecraft to be powered by the sequential release of ten million bombs.

Orion, they argued, was simple, capacious, and above all affordable.

I would love to see the more expensive option. Even paying "only" $1 million per nuclear bomb, that works out to $10,000,000,000,000.00 (ten trillion). 40-million-ton spacecraft not included, some assembly required.

A lot of people claim that the reason why the US doesn't use nuclear power everywhere is because of environmentalist whackos. This is not true. The reason is economics.

Back in the 50's when nuclear power was first proposed, people talked about having electricity too cheap to meter. The thing they did not consider is that a nuclear power plant costs much more to build than a coal/oil/natural gas plant. I want to make sure everyone understands why.

First of all, the radiation given off by fission destroys inorganic materials just as happily as it destroys human tissue. Very high quality metal must be used in all parts of the reactor to prevent degradation and to prevent it from becoming highly radioactive. This is even more of a problem in fusion reactors which have a much higher flow of neutrons, and in those, the only solution will be to replace the pieces every so often.

Second, the plant must be extremely highly reliable. One reason for this is draconian public safety regulations. However you have to keep in mind that even an accident that is contained within the plant and poses no risk to the public (a la Three Mile Island) can still destroy the reactor and put the plant out of commission.

This is true because of a property of the nuclear chain reaction. Dropping all of the control rods (scramming) does not instantly shut down the reaction in the way that dousing a coal fire would extinguish it. The reactor will continue to produce heat for around an hour after it is shut down. This means that it must be cooled for that hour, otherwise it will melt and flood the building with radioactive chemicals. The Chernobyl accident was caused by an attempt to test what happens if the cooling system is disabled.

So the system has to be very highly redundant, in part to protect the public, but mostly to protect the plant.

The last problem is that if the coolant is radioactive, you can't just call in a plumber to fix the leak as you might in a coal plant. See the movie K-19 Widowmaker for the effects of radioactive coolant on humans. You better make damn sure that system doesn't leak in the first place.

So the plants are expensive. This means you want economy of scale and build one large plant instead of many small ones. This means you don't want to build these plants in the Midwest where that much power just isn't useful. You want to build them near population centers. That explains why there is no nuclear power in sparsely populated places.

The other thing is that even though uranium is much cheaper than coal per joule (because you need so much less of it), the cost of the nuclear plant makes the whole process expensive enough that it has to compete with coal for the market. This means that in places where coal is cheap (as in the United States) building nuclear plants is only sensible up to a point. As the nuclear plants drive down demand for coal, the coal gets cheaper, so there is a natural feedback mechanism.

In the United States, we are a little bit below the optimal balance. We could economically build more nuclear plants but not that many. This difference is in part accounted for by the public perception of nuclear power.

It is also accounted for by the fact that it takes ten years to build a nuclear power plant, so if you have an energy crisis NOW, building a nuclear power plant is no good. California had to go with building natural gas power plants after their energy crisis because they are cheap and fast to build. Natural gas is more expensive but that's life.

Now it should be clear why France and Japan, two countries that use nuclear power for most of their needs, are able to do so while the US cannot. It has nothing to do with progressive governments or the lack of environmentalists. It is simply that France and Japan are small, densely populated countries (compared to the US) that have expensive coal (compared to the US). So they have a lot of nuclear plants (compared to the US).

Everybody knows that the environmental folks would pitch a fit if we tried to launch a fission-based spacecraft. But they already hate President Bush as it is, so he could include a proposal for a new fission-based shuttle replacement tomorrow and it won't get them any more angry at him than they are now (I mean, is it possible?).

And President Bush could even help handle crowd control at the launch site as well! Let's say we're launching from Cape Canaveral. During that week, Bush flies off to... say... Amundsen-Scott [nsf.gov], muttering phrases like "oil exploration," "WTO" and "nukuler." Maybe suggest he's going to do something that will kill off the ultra-rare Antarctic Dodo. Those myopic protesters that don't die of an instant embolism upon hearing of it will then take off after him, leaving the Cape nearly deserted for lift-off.

As far as I can see the glass is supposed to not absorb the 80GW of light, yet the hydrogen is. Is the author claiming that silca glass absorbs less photons than hydrogen? If it absorbed only 0.01% of the total photons it would still get 8MW of heat, which is going to be quite hard to keep cool. For comparison, the optics used in cameras absorb 0.1% of the incoming photons.

On the other hand, hydrogen doesn't strike me as particularly absorbent. I thought it was mostly transparent except for a few frequencies (the hydrogen bands). As the gas reactor is acting as a purely blackbody radiator it's going to emit in a classical SB distribution, which will mean that most photons are going to just bounce around until they get absorbed by the mirror or glass.

So the obvious problem to me (and let's face it, I'm not a rocket scientist..) is that you have an 'impedance mismatch' between your energy source and your energy sink.

You're quite wrong.:-) The Orion was originally intended for launches from some remote area. The nuclear pulsing could blast just about any weight into orbit, then take that same weight around the solar system. When various treaties banned the use of nuclear weapons on the ground, Orion switched to space only mode. Then they banned space-based bombs and Orion became a dead-duck.